Lol.
Not every purchase, thats nowhere near what I said.
I said more likely. Just like they are more likely to be paid under the table. It's not hard to understand, it's not even up for debate. In fact, even reputable places will knowingly employ illegals and pay them under the table.
Many moons ago I was in high school, at 15yo I was working my first actual job at a high end Italian grocery market. This grocery chain was the standardbearer for organic, local, fancy-pants whatever, they had about 20 locations and now they have dozens more and wayyy back then they had annual sales approaching a billion dollars. They had sponsorship deals with the MLB and NBA teams in my city and won award after award as a best place to work, for the quality of food etc etc. Even at this place which underwent countless inspections for everything you could imagine from health to employee-employer relation compliance nearly the entire seafood market division, approximately a hundred employees, were illegals from mexico who were paid in cash and still are. In fact the guy who was the district seafood manager (who is a citizen) was the fella who woukd arrange to get the labor from Mexico, and of course, they were all his "cousins". Guess what, none of them owned houses despite being 18-35yo employed adults. Most of them rented, (or more accurately "stayed") and paid in cash to live in over-crowded houses with multiple family members. And when one of his "cousins" was deported or moved back to Mexico, the owners would just ask him if he had another "cousin" who needed work. That aside, he is a nice guy, in fact we still get together now and then to watch boxing or UFC events. But I digress...
When I talk about cash transactions it would mostly be for things like auto repairs, handy projects around the house, and especially childcare. Again, it is a point of pride, especially in the illegal latino community to keep that money away from Uncle Sam. There are even credit unions and wire transfer businesses in these communities that straight up will let latinos cash checks for free but will charge black or white customers.
Mind you, these are the people who get assistance for utilities, healthcare and whatever else you can imagine, usually coordinated by social workers and community centers dedicated to helping illegals.
And you know whats really, really, funny, there is a huge black market for goods like clothing and groceries. Ever hear of people selling their foodstamps? Boosters that steal expensive grocery items and resell them? Ever seen a guy pushing a shopping cart full of socks, t-shirts and boxers, selling them 2 for 5? It exists. I don't know your experience or where you grew up, but in any city, you can find these things happening and a lot of people, entire neighborhoods, get by via buying and selling goods this way.
But please tell me more about how this isn't really happening.